This disclosure is directed to new and improved methods and systems that mitigate the effect of large amplitude, long width jamming (“J”) pulses on data transmitted between coherent data communication system transceivers.
Coherent systems refer to radio transmission systems that employ binary phase-shifted keyed (“PSK”) binary data modulation systems, coherent quadrature PSK (“QPSK”) systems and two-channel PSK systems, for example. The J pulse mitigation methods and systems herein pertain to environments wherein the power level of a J pulse burst interference signal is, for example, a hundred times the power level of data signals transmitted between a calling coherent system transceiver and a called coherent system transceiver.
Coherent radio communication methods and systems, including the specifically identified types, employ a plurality of well-known digital signal processing elements arranged in known sequences. See, FIG. 1.
The prior art coherent radio communication system of FIG. 1 includes transceivers 1 and 2 that transmit a message between them using the transmitter half Tx1 of transceiver 1 and the receiver half Rx2 of transceiver 2.
The message processing elements of the transmitter half Tx1 include:
(1) Multiplexer (“MUX”) Tx1a for forwarding a digital data message comprising binary bits to a calling party over one of several radio channels managed by MUX Tx1a to a called party accessible over an addressed channel among multiple channels managed by de-multiplexer Rx2h of receiver Rx2;
(2) data encrypter (“ENCRYPT”) Tx1b for encrypting the message to allow only authorized receivers access to the message;
(3) differential PSK data encoder (“DE”) Tx1c for encoding the encrypted message received from the encrypter into a digital form suited for transmission over a radio transmission channel between transceivers 1 and 2 created by one transceiver calling or addressing the other;
(4) forward error correction (“FEC”) encoder Tx1d, for example, a Reed-Solomon (“RS”) encoder for dividing the digital data message stream into blocks that are then encoded by adding parity bits that relate only to the information in the blocks;
(5) interleaver (“I”) Tx1e follows the Reed-Solomon FEC encoder for interleaving data into the RS blocks to provide extra protection against data loss in the transmission channel. The interleaving consists of writing data into RS blocks within FEC memory in sequence but reading the data out in a different sequence such that bytes following each other in the transmitted data sequence are not from the same Reed-Solomon block of data;
(6) direct sequence spread spectrum modulator (“SSM”) Tx1f for spreading the message into multiple parts by a pseudorandom number (“PRN” or “PN”) generator wherein each part is uniquely identified by a PN code number;
(7) radio frequency transmitter Tx1g for transmitting the encrypted, differentially encoded, FEC encoded, interleaved and spread spectrum modulated message to receiver Rx2b of transceiver 2;
(8) antenna T1h for broadcasting the message at a frequency detectable by antenna Rx2a of transceiver 2 and recoverable by transceiver 2 wherein, the two antenna Tx1h and Rx2a define a transmission or communication channel between transceivers 1 and 2.
The receiver half Rx2 of transceiver 2 employs the same number of message processing elements as employed by the transmitter half Tx1 of transceiver 1 including:
(9) antenna Rx2a for detecting and forwarding a message to receiver Rx2b of transceiver 2;
(10) radio frequency receiver Rx2b for synchronizing to the incoming message and demodulating the message for mapping received message data symbols to receive message bit pairs to which downstream elements synchronize;
(11) direct sequence spread spectrum demodulator (“DSSSDM”) Rx2c for reassembling spread parts of the transmitted message according to the PN numbers assigned to receiver Rx2;
(12) de-interleaver (“DI”) Rx2d for separating the interleaved data bits from the RS encoded bits to aid the downstream FEC decoder with the recover of data lost during the transmission of the message;
(13) FEC decoder Rx2e for recovering the FEC encoded data from the RS blocks for recovering data lost during the passage of the message over the transmission channel;
(14) differential decoder Rx2f for recovering the message digital data bit pairs in an encrypted form;
(15) de-encrypter Rx2g for restoring the encrypted message to digital bit pairs comprising the message transmitted to transceiver 2 to an understandable form; and
(16) de-multiplexer Rx2h for routing the received message to a selected radio channel addressed by transmitter Tx1.
Transceivers 1 and 2 of FIG. 1 protect data from random, inadvertent interference signals found in commercial environments and from hostile J pulses of short duration. However, prior art transceivers of FIG. 1 are not equipped to protect transmitted messages from J pulses having high power levels and long pulse widths compared to the very low power level, short duration radio signals transmitted between the two prior art transceivers of FIG. 1.